All Post Offices will be open Dec. 31, but some will shorten lobby hours New Year’s Eve. Regular mail delivery for Dec. 31 will be unaffected by the change.

Many businesses close early New Year’s Eve, and the number of customers visiting Post Office lobbies greatly diminishes. As such, Post Offices in some locations will close retail operations early Dec. 31.

Revised hours will be posted at each Post Office. To obtain the phone number of a specific Post Office, customers may call 1-800-ASK-USPS. Commercial customers are asked to check with their Bulk Mail Acceptance Unit for Dec. 31 hours of operation.

Noon will be the last collection for Dec. 31 processing for mail that is deposited in Postal Service collection boxes and office building lobby receptacles.

Post Offices will be closed Jan. 1. Express Mail will be delivered New Year’s Day and regular mail delivery will resume Jan. 2.

source: USPS